Hall-effect amplifiers



June 15, 1965 A; LEGER. JR

HALL-EFFECT AMPLIFIERS Filed Nov. 22, 1961 FIG."

AMPLIFIER CURRENT SOURCE INVENTOR. ALTON LEGER, JR;

ATTORNEY.

3,189,838 HALL-EFFECT AMPLIFIERS Alton Leger, .lr., Roslyn, Pa., assignor to Honeywell Inc., a corporation of Delaware FiledNov. 22, 1961, Ser. No. 154,301 6 Claims. (Cl. 330-6) This invention relates to signal amplifiers. More specifically, the present invention relates to a Hall-effect signal amplifier.

An object of the present invention is to provide an improved Hall-effect amplifier characterized by signal isolation between input and output signals.

Another object of the present invention is to provide an improved electro-mechanical Hall-effect amplifier. v

A further object of the present invention is to provide an improved Hall-effect electro-mechanical amplifier, as set forth herein, having a simple operation and construction.

In accomplishing these and other objects, there has been provided, in accordance with the-present invention, a Hall-effect amplifier having a Hall-plate mounted transversely in a pivotally suspended high magnetic permeability armature. The armature is positioned with its ends midway between the poles of a magnetic core structure supplying a constant magnetic flux. The magnetic structure is effective to provide an exciting magnetic flux through the Hall-plate when the armature is displaced from its midpoint position. A constant-current source is used to apply a constant current to the current terminals of the Hall-plate. An input winding is mounted on the armature to produce a torque on the armature, corresponding to an applied input signal, to displace the armature from its midpoint position. A first feedback winding is also mounted on lhe armature and is connected to the output signal terminals of the Hall-plate. The feedback winding is arranged to produce a torque on the armature in response to a signal from the Hall-plate to oppose the effect of the torque of the input winding and to restore the'armature to its midpoint position. A second feedback winding is also connected to an output signal from the Hall-plate and'is arranged to increase the exciting magnetic flux through the Hall-plate to aid the first feedback winding in restoring the armature to its midpoint position. The output signal from the Hall-plate at the midpoint position of the armature is a direct representation of an input signal applied to the input winding.-

A better understanding of the present invention may be had from the following detailed description, when read in connection with the accompanying drawing, in which:

FIG. 1 is a pictorial representation of a Hall-effect amplifier embodying the present invention.

FIG. 2 is a schematic illustration of a circuit utilizing the Hall-effect amplifier shown in FIG. 1.

Referring to FIG. 1 in more detail, there is shown a Hall-effect amplifier having an armature l of a high magnetic permeability material. The armature 1 may be in the form of a bar centrally pivotally suspended by a suspension means (not shown) in a magnetic field structure. The'magnetic field structure may comprise, as shown, two U-shaped magnetic core material elements 3, 4 which ele ments are the pole pieces of a common magnetic structure energized to provide a constant magnetic flux. Thus, the element 3 is a north pole piece and the element 4 is a south pole piece with opposite polarity magnetic confronting pole faces 5, 6 and 7, 8, respectively, at the ends 'of the U-shaped structure. The U-shaped elements 3 and 4 are disposed on opposite sides of the armature 1, respectively, with the pole faces and 7 adjacent to one end of armature 1 and the pole faces 6 and 8 adjacent to the other end of the armature 1. Thus, the core elements 3 and 4 are opposite polarity magnetic pole pieces in an Patented June 15, 1965 transverse axis between the pole faces of the elerri'ents and 4 to permit a simultaneous movement of the ends of the armature 1 about the center of thearmature 1 toward opposite polarity pole faces on elements 3 and 4. A Hallplate 10 is mounted transversely in a gap in the'armature 1 to position the Hall-plate 10 in a Hall-crystal exciting relationship with any longitudinal magnetic field within the armature 1. A pair of current terminals 11 and 12 and a pair of Hall-voltage terminals 13 and 14 are flexibly connected to the Hall-plate 10.

A supporting structure 20 is mounted on the armature 1' to support thereon an input signal coil 25 and a first feed' r the Hall-plate 10 on the armature 1 with flexible connec} tions to a pair of terminals 36.

The operation of the apparatus of the present invention 7 follows:

As previously discussed, the elements 3 and 4 are pole pieces of a common magnetic structure and are arranged to produce, in response to an energizing magnetic field for the structure, opposite magnetic poles across a gap between the pole faces of the elements 3 and 4. Accordingly, the pole faces 5 and 6 of the north pole element 3 are each effective to provide a magnetic north pole, and the pole faces 7 andB of the south pole element 4are each effective to provide a magnetic south pole. The armature 1 is pivotally suspended about a central transverse axis with its ends positioned between the confronting pole faces of the first and second elements 3 and 4, respectively. The pivotal suspension of the armature 1 is arranged to allow the ends of the armature l to rotate about the midpoint pivot point. This rotation is effective to displace one end of the armature 1 toward pole face '6 of the first element 3 and the other end toward pole face 7 of the second element 4, or to displace the ends towards pole faces 5 and 8.

The Hall-plate lift is transversely mounted ina gap in the armature 1 with respect to longitudinal flux in'the armature 1. A constant current source is connected to the current terminals 111 andtlZ to supply a constant current to the Hall-plate 10. The transverse mounting of the Hall-plate 10 is effective to produce a maximum sensitivity of the Hall-plate 10 to the longitudinal magnetic field in the armature 1. Accordingly, the Hall-plate 10 is insensitive to the transverse magnetic field established directly between the core elements 3 and 4. However, any portion of this field which passes longitudinally through the armature 1 is effective to excite the Hall crystal. This portion of the magnetic field, accordingly, is effective to produce a Hall-voltage at the Hall-output terminals 13 and 14.

Any pivotal movement of the armature 1 from a position wherein the armature ends are midway between the pole faces of the core elements 3 and 4 is effective to disturb a magnetically balanced relationship which exists at the midpoint between the pole faces. It will be noted that when the armature l is midway between the pole faces no magnetic flux passes longitudinally through the armature it. This condition is the result of the opposition of sags 6 and 7. Since these fluxes would be equal and of opposite polarity, the net result. is an absence of any longitudinal flux passing through the armature l to produce an exciting magnetic fiux through the Hall-plate 10. Thus; at the midway, or magnetically balanced, position of the armature 1, there is no output signal on the Hall-output terminals 13 and 14.

The pivotal movement of the armature ll about its central transverse axis will introduce an unstable condition since the ends of the armature 1 will continue to move toward the pole faces under the urge of the attractive force of the constant magnetic field. This displacement will allow a longitudinal magnetic field to pass through the armature 1. The direction of this magnetic field will be determined by the direction of pivotal rotation of the armature ll. For example, if the armature 1 rotates to a position with its ends closer to the pole faces 6 and 7, the longitudinal magnetic flux in the armature 1 will be passed from the pole face 6, through the armature 1, to the pole face 7. The direction of the exciting flux passing through the Hall-plate 10 is effective to determine the polarity of the Hall-voltage appearing at the output terminals 13 and 14. Consequently, this position of the armature 1 is effective to produce a Hall-voltage of one polarity. Conversely, an opposite displacement ofthe armature l is effective to produce the opposite polarity of the Hall-voltage since the direction of the longitudinal magnetic flux would reverse. The magnitude of either polarity of the Hall-voltage is dependent on the strength of the exciting magnetic flux. The strength of the longitudinal magnetic fiux in the armature 1 is dependent on the separation of the ends of the armature 1 from the poles faces, Thus, since the armature 1 would be eventually attracted to a position in contact with two of the pole faces, the Hall-voltage would eventually assume a constant polarity and a maximum amplitude at the terminal position of the armature 1.

A feedback winding 26 is provided on the armature 1 to produce a magnetic field which will interact with the magnetic field from the pole piece elements 3 and 4. The output signal from the Hall-plate 10 is amplified and is applied to the feedback winding 26. The phasing of this feedback signal is arranged to produce a magnetic field to opposite the effect of the magnetic field from the elements 3 and 4. The effect of these magnetic fields may be compared to the operation of a galvanometer. The magnetic field from the elements 3 and 4 is effective to produce a torque on the armature 1 if the armature is displaced from its midpoint position. The magnetic field from the feedback winding 26 is arranged to produce a torque on the armature l which will opposite any torque resulting from the action of the element field. Accordingly, the effect of the feedback winding torque is to restore the armature 1 to the midpoint position between the pole faces of the elements 3 and 4. Thus, any movement of the armature 1 would be sensed by the Hall-plate 10 and, the resulting amplified signal would be applied to the feedback winding to restore the armature 1 to its midpoint position.

An input signal winding 25 is provided on the armature 1 and is connected to a pair of input terminals 30. A signal applied to the input winding 25 is effective to produce a magnetic field which will also interact with the magnetic field from the core elements 3 and 4. This interaction is arranged to produce a torque which will displace the armature 1 in a direction determined by the polarity of the input signal. The feedback signal from the Hall-plate 10 produced by this displacement of the armature is applied to the feedback winding 26. This signal is effective to produce a torque to counter-balance the torque produced by the input signal applied to the winding 25. The restoration of the armature 1 to the midpoint position is effective to provide an output signal from the Hall-output terminals 13, 14 which is a direct representation of the input signal applied to the input terminals 30.

- tained small displacement.

al e

In order to enhance the operation of the present invention, a second feedback winding 35 may be mounted on the armature It to provide an exciting flux for the Hallplate 10. The effect of thesecond feedback winding 35 is to overcome a possible error in the operation of the present invention resulting from the counter-balancing operation of the first feedback winding 26. The magni tude of the feedback signal, and the resulting torque, is

determined by the gain of the amplified Halhplate 10. If p this gain is not sufficiently high, the Hall-plate must produce a small output signal for amplification and applica-' tion to the feedback winding 26 to produce a torque to counterbalance the input signal torque. Accordingly, the armature 1 will not be returned to its midpoint position by winding 26 since this would eliminate any Hall-plate output signal. The required signal is, thus, produced by a sustained small displacement of the armature 1 from I its midpoint position. The torque produced by the first feed-back winding 26, accordingly, must be effective to balance the torque produced by the input winding 25 as well as the torque of the armature resulting from the sus- The output signal from the Hall-plate 10, accordingly, is not a direct representation of the input signal but includes an additional portion representing the displacement of the armature l.

The operation of the present invention as an amplifier is enhanced if this error signal in the output signal from the Hall-plate is eliminated. The elimination of this error signal is effective to allow the output signal from the Hallplate 10 to be an accurate representation of the input signal applied to the winding 25. For this purpose, the second feedback winding 35 may be provided on the armature 1 for connection to a proportional part of the amplified Hall-plate signal. This winding 35 is positioned on the'arni-ature 1 with respect to the Hall-plate 10 in a manner to produce a magnetic flux through the Hall-plate 10 but not a flux to interact with the constant magnetic field from the elements 3 and 4. This magnetic flux from the winding 35 is arranged to produce an output signal from the Hall-plate 10 which is effective, when applied to the first feedback winding 26, to aid in counterbalancing the input torque and to restore the armature l to a virtual midpoint position between the pole faces. It may be seen that the winding 35 is effective to supply an exciting flux to produce an output signal from the Hall-plate 10 even when the armature 1 is in its midpoint position. This signal when applied to the first feedback winding 26, consequently, willcontinue to produce a balance torque not dependent on the field from the elements 3 and 4 to retain the armature 1 at its midpoint position where the constant magnetic field does not supply an exciting flux to the Hall-plate 10'. The winding 35, accordingly, is effective to eliminate the possible error in the output signal from the Hall-plate caused by the aforesaid small displacement. the Hall-plate, consequently, is made to be a direct representation of the input signal applied to the input winding 25.

Accordingly, it may be seen that there has been provided in accordance with the present invention, an electromechanical Halleffect amplifier characterized by a reproduction and amplification of an input signal and signal isolation between the input signal and an output signal.

What is claimed is:

1. A Hall-effect amplifier comprising a Hall-plate having output signal terminals and current terminals, means for supplying a constant-current to said Hall-plate current terminals, magnetic field producing means for supplying a constant magnetic field, high magnetic permeability means pivotally suspended about a central transverse axis, and operatively associated with said magnetic field producing means to provide a diverting longitudinal magnetic path for said magnetic field in a displaced position of said permeability means said Hall-plate being mounted within said high permeability means transverse- The output signal from 1y to a longitudinal magnetic flux in said permeability means and parallel to said magnetic field, input signal means mounted on said high permeability means for pro ducing a magnetic field in response to an input signal to interact with said constant magnetic field to produce a torque on said permeability means, and, feedback signal means mounted on said high permeability means and connected to said output signals terminals to produce 'a magnetic field in response to an output signal from said Hallplate to interact with said constant magnetic field to produce a torque on said permeability means.

2. A'Hall-eifect amplifier comprising a Hall-plate having a pair of output signal terminals and a pair of current terminals, means for supplying a constant current to said current terminals, a high permeability armature having,

said Hall-plate mounted transversely therein with respect to a longitudinal magnetic flux in said armature, a magnetic core structure for supplying a constant magnetic -field across a characterized gap in said structure, said armature being pivotally suspended about a central transverse axis of said armature in said gap with said Hallplate being parallel to said magnetic field with said armature providing a diverting longitudinal magnetic path for said magnetic field in a displaced position of said armature in said gap, an input signal winding mounted on said armature to produce a magnetic field representative of an input signal applied to said winding, said last-men tioned fieldinteracting with said constant field to produce a torque on said armature, a feedback winding mounted on said armature, and means connecting said feedback winding with said output terminals,- said feedback winding producing a magnetic field representative of an output signal from said Hall-plate to interact with said constant field to counterbalance the torque produced by said input signal winding.

3. A Hall-effect amplifier comprising a Hall-plate having output signal terminals and current terminals, means for supplying a constant-current to said Hall-plate current terminals, magnetic field producing means for supplying a constant magnetic field, high magnetic perma ebility means pivotally suspended about a central transverse axis and opcratively associated with magnetic field producing means to provide a diverting longitudinal magnetic path for said magnetic field in a displaced position of said permeability means, said Hall-plate being mounted within said high permeability means transversely to a longitudinal magnetic flux in said permeability means and parallel to said magnetic field, input signal means mounted on said high permeability means for producing a magnetic field in response to an input signal to interact with said constant magnetic field to produce a torque on said permeabilitymeans, and feedback signal means mounted on said high permeability means and connected to said output signals terminals to produce a magnetic field in response to an output signal from said Hall-plate to interact with said constant magnetic field to produce a torque on said permeability means and to provide longitudinal flux through said permeability means.

4. A Hall-effect amplifier comprising a Hall-plate hav-- ing a pairof output signal terminals and a pair of current terminals, means for supplying a constant current to said current terminals, a high, permeability armature having said Hall-plate mounted transversely therein with respect to a longitudinal magnetic flux in magnetic path for said magnetic field in a displaced posi-' tlon of said armature in said gap, an input signal winding" mounted on said armature to produce a magnetic field representative of an input signal applied to said winding, said last-mentioned field interacting with said constant field to produce a torque on said armature, a first feed- ,back winding mounted on said armature, means connecting said feedback winding with said output terminals, said feedback winding producing a magnetic field representative of an output signal from said Hall-plate to counterbalance the torque produced by said input signal winding, a second feedback winding wound on said armature and means connecting second winding to an output signal from said Hall-plate to provide an exciting flux through said Hall-plate.

5. A Hall-effect amplifier comprising a Hall-plate having output signal terminals and current terminals, means for supplying an energizing current to said current terminals, magnetic field producing means for producing a first magnetic field, means for suspending said Hall-plate in non-exciting relationship with said magnetic field, input signal means for diverting said first magnetic field proportionally to the magnitude of an input signal applied to said input signal means to excite said Hall-plate, and feedback signal means connected to said output terminals of said Hall-plate to counterbalance the etfect of said input signal means whereby to provide an output-signal -on said output terminals corresponding to said input signal.

6. A Hall-effect amplifier comprising a Hall-plate having output signal terminals and current terminals, means for supplying an energizing current to said current terminals, magnetic field producing means for producing a first magnetic field, means for suspending said Hall-plate in non-exciting relationship with said magnetic field, input signal means for diverting said first magnetic field proportionally to the magnitude of an input signal applied to said input signal means to excite said Hall-plate, first feedback signal means connected to said output terminals of said Hall-plate to counterbalance the etfect of said input signal means and second feedback signal means connected to said output'terminals to produce an exciting flux for said Hall-plate proportional to an output signal from said Hall-plate.

References Cited by the E until-er FOREIGN PATENTS ROY LAKE, Primary Examiner.

NATHAN KAUFMAN, Examiner. 

1. A HALL-EFFECT AMPLIFIER COMPRISING A HALL-PLATE HAVING OUTPUT SIGNAL TERMINALS AND CURRENT TERMINALS, MEANS FOR SUPPLYING A CONSTANT-CURRENT TO SAID HALL-PLATE CURRENT TERMINALS, MAGNETIC FIELD PRODUCING MEANS FOR SUPPLYING A CONSTANT MAGNETIC FIELD, HIGH MAGNETIC PERMEABILITY MEANS PIVOTALLY SUSPENDED ABOUT A CENTRAL TRANSVERSE AXIS, AND OPERATIVELY ASSOCIATED WITH SAID MAGNETIC FIELD PRODUCING MEANS TO PROVIDE A DIVERTING LONGITUDINAL MAGNETIC PATH FOR SAID MAGNETIC FIELD IN A DISPLACED POSITION OF SAID PERMEABILITY MEANS SAID HALL-PLATE BEING MOUNTED WITHIN SAID HIGH PERMEABILITY MEANS TRANSVERSELY TO A LONGITUDINAL MAGNETIC FLUX IN SAID PERMEABILITY MEANS AND PARALLEL TO SAID MAGNETIC FIELD, INPUT SIGNAL MEANS MOUNTED ON SAID HIGH PERMEABILITY MEANS FOR PRODUCING A MAGNETIC FIELD IN RESPONSE TO AN INPUT SIGNAL TO INTERACT WITH SAID CONSTANT MAGNETIC FIELD TO PRODUCE A TORQUE ON SAID PERMEABILITY MEANS, AND FEEDBACK SIGNAL MEANS MOUNTED ON SAID HIGH PERMEABILITY MEANS AND CONNECTED TO SAID OUTPUT SIGNALS TERMINALS TO PRODUCE A MAGNETIC FIELD IN RESPONSE TO AN OUTPUT SIGNAL FROM SAID HALLPLATE TO INTERACT WITH SAID CONSTANT MAGNETIC FIELD TO PRODUCE A TORQUE ON SAID PERMEABILITY MEANS. 